Inhibition of corrosion of SS 18/8 alloy is sea water by Thiourea-Zn2+ system

Abstract

The corrosion resistance of SS 18/8 in natural sea water, in presence of an inhibitor named Thiourea-Zn2+ has been evaluated. Weight loss method, polarization study and AC impedance spectra have been employed to evaluate the corrosion resistance of SS 18/8 alloy in natural sea water, in presence of an inhibitor named Thiourea-Zn2+ system. Weight loss method reveals that Thiourea-Zn2+ system offers a maximum corrosion inhibition efficiency of 95% in controlling corrosion of SS 18/8 alloy in natural sea water. Synergism parameters are found to be greater than 1, confirming the synergistic effect existing between Thiourea-Zn2+. Adsorption of inhibitor molecules on the metal surface obey Langmuir adsorption isotherm. Polarisation study reveals that the inhibitors named Thiourea-Zn2+ system functions as mixed type of inhibitor. AC impedance spectra confirm the formation of a protective film on the metal surface. This formulation of Thiourea-Zn2+ may be used in cooling water systems where SS 18/8 alloy pipelines are used to carry sea water which is used as coolant. Also, Thiourea-Zn2+ coating can be given on SS 18/8 alloy to protect it from corrosion by sea water when SS 18/8 alloy is used as hull plates in ship industry.